"HP has strict policies in place that require contractors and their employees to adhere to the highest standards of business practices and ethics," the company said in a statement about its termination of The Experts, a Florida information technology firm.

"Based on what we now know about The Experts' conduct, including its failure to respond appropriately to Aaron Alexis' mental health issues and certain incidents recently reported in the press, HP has terminated its relationship with The Experts."

HP had confirmed last week that Alexis had worked for The Experts, a Florida based subcontractor, on the firm's government contract to refresh and replace computers on a Navy-Marine Corps intranet network at the Navy Yard. Alexis, a former petty officer, killed 12 people and wounded four more before he died in a shootout with officers at the Naval Sea Systems Command headquarters.

In a letter obtained by NBC News, an HP executive wrote Thomas Hosko, chief executive officer of The Experts, on Wednesday saying it "has lost all confidence in The Experts ability to meet its contractual obligations and serve as an HP subcontractor." As a result, HP said, it was terminating its contract with the firm within 30 days.

FBI via AP

Aaron Alexis

HP declined to specify what it believed The Experts' lapses were, but the statement came shortly after the FBI disclosed that Alexis had been suffering from a "delusional" belief that he was being controlled by "low frequency electro-magnetic waves. "

Rhode Island police had said last week it had reported raising concerns with the Navy last August after Alexis called them to complain he was "hearing voices" and believed he was under surveillance while working on another job for The Experts in that state.

A spokeswoman for The Experts, said in response: "The Experts is disappointed in H-P's decision, as we have continued to meet all of our contractual obligations. The Experts had no greater insight into Alexis' mental health than H-P, particularly given that an H-P site manager closely supervised him, including during the events in Rhode Island."